Desktop speakerphones are well-known devices that allow groups of people to simultaneously converse in a conference mode using a single telephone and telephone connection. Desktop speakerphones also allow individual users to conduct hands-free conversations.
Traditional speakerphones have one or more built-in, fixed microphones. When used in a conference call mode, such speakerphones experience large differences in the distance between the microphone and talkers within the room. As a result, the level of a distant talker's voice at the microphone can fall low enough that the speech processing algorithms used in the speakerphone to suppress or eliminate echo can cause significant distortion to the speech or may even eliminate it entirely.
Traditional speakerphones also have a distinctive “speakerphone sound”, sometimes referred to as “barrel sound” imposed on the near talker's voice if there is a large distance between the near talker's mouth and the microphone. This results from the talker's voice reaching the microphone both by a direct, line-of-sight path also via multiple reflected paths resulting from the room's walls and contents. The further the talker is from the microphone, the larger the contribution from the reflected paths and the greater the reverberation or “barrel sound”.
Additionally, the far party may hear echoes of their voice if the speakerphone is not perfect and fails to suppress or cancel the echo. This echo is more prevalent in speakerphones that attempt to provide full-duplex communications. This also means that even an individual user of such a speakerphone, conducting a hands-free conversation, must avoid excessive motion when near to the microphone. Echo suppression or cancellation is easier when the acoustic coupling between the microphone and the loudspeaker is low. In traditional speakerphones the microphone and loudspeaker are close together, resulting in relatively high acoustic coupling between them and making the echo suppression or canceling more difficult.
These shortcomings of traditional speakerphones can be very distracting to the party or parties on the far end of the telephone conversation.
Prior art attempts to solve these problems, such as U.S. Pat. No. 5,748,707 to Sanserino entitled “Speakerphone with remote microphone having speaker cut-off for half duplex operation”, U.S. Pat. No. 5,832,390 to Irvin entitled “Untethered microphone and base unit” and U.S. Pat. No. 6,321,080 to Diethorn entitled “Conference telephone utilizing base and handset transducers”, all of which are hereby incorporated by reference, do not provide for the remote microphone to additionally be attached in a wired mode which is more secure against electronic eavesdropping.
There is a need for a telephone that can switch between operating as a conventional, secure speakerphone to operating in a speakerphone mode that facilitates conference calls but avoids the shortcomings of traditional speakerphones described above, including the so called “barrel sound” and unwanted echoing.